The mechanical restoration of 17th-century books requires a specialized synthesis of historical engineering and contemporary material science. During the 1600s, the production of vellum-over-board bindings reached a peak of structural complexity, necessitating the development of strong wooden presses to manage the high tension and hygroscopic nature of animal-skin substrates. Modern conservation of these artifacts focuses on stabilizing the chemical and physical integrity of vellum, paper, and adhesives using techniques that mirror the precision of the original bookbinders while employing advanced stabilization agents.
The preservation of these historical volumes is not merely an aesthetic try but a rigorous technical discipline. It involves the analysis of degradation pathways in organic materials, such as the hydrolysis of hide glues and the oxidative browning of cellulose fibers. Conservators must handle the reactive properties of 17th-century inks, which often contain iron-gall components that can catalyze the degradation of the underlying paper. The following study examines the mechanical tools and chemical protocols essential to the maintenance of these seventeenth-century objects.
What changed
In the transition from the late 16th to the 17th century, the mechanical approach to book compression evolved from rudimentary weighted systems to the sophisticated screw-driven standing press. This shift allowed for a more uniform application of force, which was critical for the successful adhesion of vellum to wooden or pasteboard substrates. The primary developments in this era included:
- Precision of the Screw Thread:The introduction of more accurately carved wooden and occasionally metal screws allowed for incremental pressure adjustments, reducing the risk of crushing the book's shoulder or damaging the delicate sewing structure.
- Platen Stability:The design of the platen—the flat plate that applies pressure—was modified to include reinforcements that prevented bowing, ensuring that the edges and the center of the book block received equal compressive force.
- Specialization of the Laying Press:While earlier binders used multipurpose clamps, the 17th century saw the refinement of the laying (or finishing) press, which utilized twin screws to hold a volume vertically for edge-trimming, backing, and the application of headbands.
- Integration of Material Science:Binders began to recognize the distinct drying rates of different wood types, leading to the use of seasoned hardwoods like oak and fruitwood in press construction to minimize structural shifting caused by atmospheric humidity.
Background
The technical standards for 17th-century bookbinding mechanics were most notably documented by Joseph Moxon in his 1683 treatise,Mechanick Exercises: Or, the Doctrine of Handy-Works. Moxon provided detailed diagrams and instructions for the construction of the standing press and the finishing press, which remain the blueprints for historical reconstructions used in modern conservation labs. The 17th-century bindery was a site of high-precision manual labor, where the physics of use and torque were applied to the organic chemistry of animal products.
Vellum, a non-tanned skin prepared by soaking in lime and drying under tension, was the preferred covering material for high-status and durable volumes. However, vellum is exceptionally sensitive to environmental changes; it expands and contracts with greater force than leather or paper. The 17th-century press was designed to counteract this movement during the critical drying phase. If the pressure was uneven, the vellum would warp the boards, leading to a permanent distortion of the codex. Consequently, the engineering of the press was inextricably linked to the biological properties of the skin it was designed to contain.
The Mechanics of the Wooden Standing Press
The 17th-century standing press was a large timber frame consisting of a heavy base, two upright cheeks, and a massive top cross-beam known as the "head." The central screw passed through the head and was attached to a moving platen. According to Moxon’s specifications, the screw was typically fashioned from oak for its density and resistance to shear stress. The physics of this device relied on the mechanical advantage of the screw thread; a binder could generate several tons of force using a long wooden bar (the "press-pin") inserted into the head of the screw.
For vellum-over-board bindings, the distribution of this force was critical. Vellum requires a slow, controlled drying process. If the pressure is released too early, the skin’s natural memory will cause it to curl. The use of adjustable platens allowed conservators and historical binders to maintain an even load across the entire surface of the book. In modern restoration, custom-fabricated versions of these presses include micro-adjustable platens to account for the irregular thickness often found in aged vellum and handmade papers.
Material Science in Press Fabrication
The choice of timber for press construction was a critical engineering decision. Oak was the standard for the frame because of its longitudinal strength. However, for the components in direct contact with the moisture of the binding process—the platens and the press-boards—fruitwoods like pear, cherry, or apple were often preferred. These woods have a finer grain and are less prone to "checking" or warping when exposed to the moisture of animal glues (hide glue and parchment paste).
Animal glues are hygroscopic, meaning they absorb water from the air. During the drying process, as water evaporates, the glue undergoes significant shrinkage. A press made of inferior or unseasoned wood would warp alongside the book, resulting in an uneven finish. The use of dense, seasoned hardwoods ensured that the press remained a stable, inanimate reference point against which the volatile organic materials of the book could settle.
Restoration and Conservation Protocols
Modern restoration of 17th-century volumes utilizes the mechanical principles of the past alongside contemporary chemical stabilization. When a volume suffers from delamination or brittle failure, the conservator must intervene with surgical precision. This involves several distinct phases of treatment, often requiring weeks of controlled pressing.
Aqueous Deacidification and Consolidation
Paper components within 17th-century bindings often suffer from acidity, which breaks down the cellulose chains. Treatment protocols often involve aqueous deacidification using buffered solutions of calcium bicarbonate or magnesium bicarbonate. This process neutralizes existing acids and leaves an alkaline reserve in the paper to protect against future degradation. Following deacidification, brittle fibers are consolidated usingKLUCEL G(hydroxypropylcellulose), a reversible synthetic adhesive. Klucel G is typically applied in an ethanol or isopropanol base, which allows it to penetrate the fibers and provide structural reinforcement without the distorting effects of water.
Vellum Stabilization and Re-sewing
The restoration of the vellum cover itself requires an acute visual acuity for detecting subtle signs of deterioration, such as "red rot" (though more common in leather) or parchment glassification. To treat delaminated layers of vellum, conservators use micro-spatulas to carefully lift the skin and apply a parchment-size or a dilute rabbit-skin glue. Once the adhesive is applied, the volume is returned to the press to ensure the layers bond flatly.
If the original sewing has failed, the signatures must be re-sewn onto historically appropriate cords or slips. This is done using unbleached linen thread that has been treated with beeswax. The beeswax serves two mechanical functions: it minimizes friction during the sewing process, preventing the thread from cutting through the aged paper, and it provides a moisture barrier that enhances the durability of the structural assembly. The re-sewn block is then reintegrated into the vellum casing, utilizing the standing press to ensure the entire assembly achieves a unified structural integrity.
Tools of the Modern Conservator
While the heavy mechanics are handled by the press, the fine-scale work requires specialized hand tools. These include:
- Fine Bone Folders:Crafted from polished cattle bone or Teflon, these are used to achieve precise creasing and to burnish the vellum without abrading the surface.
- Micro-Spatulas:Stainless steel tools used for the controlled application of adhesives and the lifting of fragile paper layers.
- Adjustable Press-Boards:Modern boards made from high-density laminates or acrylics that do not warp and provide a perfectly flat surface for the book block.
The ultimate objective in the restoration of 17th-century vellum bindings is a balance between stabilization and authenticity. By employing the mechanical logic of 1683 with the chemical knowledge of the 21st century, conservators ensure that these artifacts remain functional and historically accurate for future study. The precision of the press remains the cornerstone of this discipline, acting as the primary tool for correcting the centuries of movement inherent in organic, artisanal materials.
